Process for making a low density detergent composition by controlling agglomeration via particle size

ABSTRACT

A process for preparing low density detergent agglomerates is provided. The process involves the step of: (a) agglomerating a detergent surfactant paste or precursor thereof and dry starting detergent material having a median particle size in a range from about 5 microns to about 70 microns in a first high speed mixer to obtain detergent agglomerates having a median particle size of from about 100 microns to about 250 microns; (b) mixing the detergent agglomerates with a binder in a second high speed mixer to obtain built-up agglomerates having a median particle size in a range of from 140 microns to about 350 microns; and (c) feeding the built-up agglomerates into a fluid bed dryer in which the built-up agglomerates are agglomerated with another binder and dried to form detergent agglomerates having a median particle size in a range from about 300 microns to about 700 microns and a density in a range from about 300 g/l to about 550 g/l.

This application claims the benefit of U.S. Provisional application Ser.No. 60/052,412, filed Jul. 14, 1997.

FIELD OF THE INVENTION

The present invention generally relates to a process for producing a lowdensity detergent composition. More particularly, the invention isdirected to a process during which low density detergent agglomeratesare produced by feeding a surfactant paste or liquid acid precursor ofanionic surfactant and dry starting detergent material sequentially intotwo high speed mixers followed by a fluid bed dryer. The processproducts a free flowing, low density detergent composition which can becommercially sold as a conventional non-compact detergent composition orused as an admix in a low dosage, “compact” detergent product.

BACKGROUND OF THE INVENTION

Recently, there has been considerable interest within the detergentindustry for laundry detergents which are “compact” and therefore, havelow dosage volumes. To facilitate production of these so-called lowdosage detergents, many attempts have been made to produce high bulkdensity detergents, for example with a density of 600 g/l or higher. Thelow dosage detergents are currently in high demand as they conserveresources and can be sold in small packages which are more convenientfor consumers. However, the extent to which modern detergent productsneed to be “compact” in nature remains unsettled. In fact, manyconsumers, especially in developing countries, continue to prefer ahigher dosage levels in their respective laundering operations.Consequently, there is a need in the art of producing modern detergentcompositions for flexibility in the ultimate density of the finalcomposition.

Generally, there are two primary types of processes by which detergentgranules or powders can be prepared. The first type of process involvesspray-drying an aqueous detergent slurry in a spray-drying tower toproduce highly porous detergent granules. In the second type of process,the various detergent components are dry mixed after which they areagglomerated with a binder such as a nonionic or anionic surfactant. Inboth processes, the most important factors which govern the density ofthe resulting detergent granules are the density, porosity and surfacearea, shape of the various starting materials and their respectivechemical composition. These parameters, however, can only be variedwithin a limited range. Thus, flexibility in the substantial bulkdensity can only be achieved by additional processing steps which leadto lower density of the detergent granules.

There have been may attempts in the art for providing processes whichincrease the density of detergent granules or powders. Particularattention has been given to densification of spray-dried granules bypost tower treatment. For example, one attempt involves a batch processin which spray-dried or granulated detergent powders containing sodiumtripolyphosphate and sodium sulfate are densified and spheronized in aMarumerizer®. This apparatus comprises a substantially horizontal,roughened, rotatable table positioned within and at the base of asubstantially vertical, smooth walled cylinder. This process, however,is essentially a batch process and is therefore less suitable for thelarge scale production of detergent powders. More recently, otherattempts have been made to provide continuous processes for increasingthe density of “post-tower” or spray dried detergent granules.Typically, such processes require a first apparatus which pulverizes orgrinds the granules and a second apparatus which increases the densityof the pulverized granules by agglomeration. While these processesachieve the desired increase in density by treating or densifying “posttower” or spray dried granules, they do not provide a process which hasthe flexibility of providing lower density granules using anagglomeration process or other non-tower process.

Moreover, all of the aforementioned processes are directed primarily fordensifying or otherwise processing spray dried granules. Currently, therelative amounts and types of materials subjected to spray dryingprocesses in the production of detergent granules has been limited. Forexample, it has been difficult to attain high levels of surfactant inthe resulting detergent composition, a feature which facilitatesproduction of detergents in a more efficient manner. Thus, it would bedesirable to have a process by which detergent compositions can beproduced without having the limitations imposed by conventional spraydrying techniques.

To that end, the art is also replete with disclosures of processes whichentail agglomerating detergent compositions. For example, attempts havebeen made to agglomerate detergent builders by mixing zeolite and/orlayered silicates in a mixer to form free flowing agglomerates. Whilesuch attempts suggest that their process can be used to producedetergent agglomerates, they do not provide a mechanism by whichconventional starting detergent materials in the form of surfactantpastes or precursors thereof, liquids and dry materials can beeffectively agglomerated into crisp, free flowing detergent agglomerateshaving low densities rather than high densities. In the past, attemptsat producing such low density agglomerates involves a nonconventionaldetergent ingredient which is typically expensive, thereby adding to thecost of the detergent product. One such example of this involves aprocess of agglomerating with inorganic double salts such as Burkeite toproduce the desired low density agglomerates.

Accordingly, there remains a need in the art to have a process forproducing a low density detergent composition directly from startingdetergent ingredients without the need for relatively expensivespecialty ingredients. Also, there remains a need for such a processwhich is more efficient, flexible and economical to facilitatelarge-scale production of detergents of low as well as high dosagelevels.

BACKGROUND ART

The following references are directed to densifying spray-driedgranules: Appel et al, U.S. Pat. No. 5,133,924 (Lever); Bortolotti etal, U.S. Pat. No. 5,160,657 (Lever); Johnson et al, British patent No.1,517,713 (Unilever); and Curtis, European Patent Application 451,894.The following references are directed to producing detergents byagglomeration: Beerse et al, U.S. Pat. No. 5,108,646 (Procter & Gamble);Capeci et al, U.S. Pat. No. 5,366,652 (Procter & Gamble); Hollingsworthet al, European Patent Application 351,937 (Unilever); and Swatling etal, U.S. Pat. No. 5,205,958. The following references are directed toinorganic double salts: Evans et al, U.S. Pat. No. 4,820,441 (Lever);Evans et al, U.S. Pat. No. 4,818,424 (Lever); Atkinson et al, U.S. Pat.No. 4,900,466 (Lever); and France et al, U.S. Pat. No. 5,576,285(Procter & Gamble); and Dhalewadika et al, PCT WO 96/04359 (Unilever).

SUMMARY OF THE INVENTION

The present invention meets the aforementioned needs in the art byproviding a process which produces a low density (below about 600 g/l)detergent composition directly from starting ingredients without theneed for certain relatively expensive specialty ingredients. The processdoes not use the conventional spray drying towers currently used and istherefore more efficient, economical and flexible with regard to thevariety of detergent compositions which can be produced in the process.Moreover, the process is more amenable to environmental concerns in thatit does not use spray drying towers which typically emit particulatesand volatile organic compounds into the atmosphere. In essence, theprocess involves agglomerating a surfactant paste or precursor thereofand dry detergent ingredients in a high speed mixer followed by anotherhigh speed mixer to form agglomerates which have been built-up or gluedtogether via controlled particle size growth such that the resultingagglomerates are highly porous and have a very low density. The built-uplow density agglomerates are further agglomerated in this fashion anddried in a fluid bed dryer to produce the final low density detergentagglomerates.

As used herein, the term “agglomerates” refers to particles formed byagglomerating detergent granules or particles which typically have asmaller median particle size than the formed agglomerates. Allpercentages used herein are expressed as “percent-by-weight” on ananhydrous basis unless indicated otherwise.

In accordance with one aspect of the invention, a process for preparinglow density detergent agglomerates is provided. The process comprisesthe steps of: (a) agglomerating a detergent surfactant paste orprecursor thereof and dry starting detergent material having a medianparticle size in a range from about 5 microns to about 70 microns in afirst high speed mixer to obtain detergent agglomerates having medianparticle size of from about 100 microns to about 250 microns; (b) mixingthe detergent agglomerates with a first binder in a second high speedmixer to obtain built-up agglomerates having a median particle size in arange of from about 140 microns to about 350 microns; and (c) feedingthe built-up agglomerates into a fluid bed dryer in which the built-upagglomerates are agglomerated with a second binder and dried to formdetergent agglomerates having a median particle size in a range of fromabout 300 microns to about 700 microns and a density in a range fromabout 300 g/l to about 550 g/l.

In accordance with another aspect of the invention, another process forpreparing low density detergent agglomerates is provided. The processcomprises the steps of: (a) agglomerating a first liquid acid precursorof an anionic surfactant and dry starting detergent material having amedian particle size in a range from about 5 microns to about 50 micronsin a first high speed mixer to obtain detergent agglomerates having amedian particle size of from about 100 microns to about 250 microns; (b)mixing the detergent agglomerates with a second liquid acid precursor ofan anionic surfactant in a second high speed mixer to obtain built-upagglomerates having median particle size in a range of from about 140microns to about 350 microns; and (c) feeding the built-up agglomeratesinto a fluid bed dryer in which the built-up agglomerates areagglomerated with a third liquid acid precursor of an anionic surfactantand dried to form detergent agglomerates having a median particle sizein a range of from about 300 microns to about 700 microns and a densityin a range from about 300 g/l to about 550 g/l. The detergent productsmade in accordance with any of the process embodiments described hereinare also provided.

Accordingly, it is an object of the invention to provide a process forproducing a low density detergent composition directly from startingdetergent ingredients which does not include relatively expensivespecialty ingredients. It is also an object of the invention to providesuch a process which is more efficient, flexible and economical so as tofacilitate large-scale production of detergents of low as well as highdosage levels. These and other objects, features and attendantadvantages of the present invention will become apparent to thoseskilled in the art from a reading of the following detailed descriptionof the preferred embodiment and the appended claims.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention is directed to a process in which low densityagglomerates are produced by controlling the median particle size of thedetergent ingredients in every step of the process. By “median particlesize”, it is meant the particle size diameter value above which 50% ofthe particles have a larger particle size and below which 50% ofparticles have a smaller particle size. The process forms free flowing,low density detergent agglomerates which can be used alone as thedetergent product or as an admixture with conventional spray-drieddetergent granules and/or high density detergent agglomerates in a finalcommercial detergent product. It should be understood that the processdescribed herein can be operated continuously or in a batch modedepending upon the particularly desired application. One major advantageof the present process is that it utilizes equipment currently used tomake high density or compact detergent products. However, the processdescribed herein produces low density detergent compositions from suchsimilar equipment by selectively adjusting and modifying certain unitoperations and parameters as detailed herein. In this way, a singlelarge-scale commercial detergent manufacturing facility can be built toproduce high or low density detergent compositions depending upon thelocal consumer demand and its inevitable fluctuations between compactand non-compact detergent products.

Process

In the first step of the process, a detergent surfactant paste orprecursor thereof as set forth in more detail hereinafter and drystarting detergent material having a selected median particle size isinputted and agglomerated in a high speed mixer. Unlike previousprocesses in this area, the dry starting material can include only thoserelatively inexpensive detergent materials typically used in moderngranular detergent products. Such ingredients, include but are notlimited to, builders, fillers, dry surfactants, and flow aides.Preferably, the builder includes aluminosilicates, crystalline layeredsilicates, phosphates, carbonates and mixtures thereof which is theessential dry starting detergent ingredient within the scope of thecurrent process. Relatively expensive materials such as Burkeite(Na₂SO₄.Na₂CO₃) and the various silicas are not necessary to achieve thedesired low density agglomerates produced by the process. Rather, it hasbeen found that by judiciously controlling the median particle size ofthe inputted dry materials, particle build-up can be achieved in mannerwhich produces agglomerates having a high degree of “intraparticle” or“intragranule” or “intraagglomerate” porosity, and therefore are low indensity. The terms “intraparticle” or “intragranule” or“intraagglomerate” are used synonmously herein to refer to the porosityor void space inside the formed built-up agglomerates produced at anystage of the process.

Accordingly, in the first step of the process, the median particle sizeof the dry detergent material if preferably in a range from about 5microns to about 70 microns, more preferably from about 10 microns toabout 60 microns, and most preferably from about 10 microns to about 50microns. It is also preferable to include from 1% to about 40% by weightof recycled undersized detergent particles or “fines” in the first stepof the process. This can be conveniently accomplished by screening thedetergent particles formed subsequent to the fluid bed dryer to a medianparticle size range of from about 10 microns to about 150 microns andfeeding these “fines” back into the first high speed mixer.

The high speed mixer can be any one of a variety of commerciallyavailable mixers such as a Lödige CB 30 mixer or similar brand mixer.These types of mixers essentially consist of a horizontal, hollow staticcylinder having a centrally mounted rotating shaft around which severalshovel and rod-shaped blades are attached which have a tip speed of fromabout 5 m/s to about 30 m/s, more preferably from about 6 m/s to about26 m/s. At the scale of a Lödige CB 30, the shaft rotates at a speed offrom about 100 rpm to about 2500 rpm, more preferably from about 300 rpmto about 1600 rpm. At other mixer scales, the preferred rotation speedis adjusted to maintain tool tip speed equivalent to that of the LödigeCB 30. The tip speed is calculated by multiplying the radius from thecenter of the shaft to the tool tip by 2 πN, wherein N is the rotationspeed. Preferably, the mean residence time of the detergent ingredientsin the high speed mixer is preferably in range from about 2 seconds toabout 45 seconds, and most preferably from about 5 seconds to about 15seconds. This mean residence time is conveniently measured by dividingthe weight of the mixer at steady state by throughput (kg/hr) flow.Another suitable mixer is any one of the various Flexomix modelsavailable from Schugi (Netherlands) which are vertically positioned highspeed mixers. This type of mixer is preferably operated at a FroudeIndex of from about 13 to about 32. See U.S. Pat. No. 5,149,455 toJacobs et al (issued Sep. 22, 1992) for a detailed discussion of thiswell-known Froude Index which is a dimensionless number that can beoptimally selected by those skilled in the art.

In a preferred embodiment of the process invention, a liquid acidprecursor of an anionic surfactant is inputted with the dry startingdetergent material which at least includes a neutralizing agent such assodium carbonate. The preferred liquid acid surfactant precursor isC₁₁₋₁₈ linear alkylbenzene sulfonate surfactant (“HLAS”), although anyacid precursor of an anionic surfactant may be used in the process. Amore preferred embodiment involves feeding a liquid acid precursor ofC₁₂₋₁₄ linear alkylbenzene sulfonate surfactant with a C₁₀₋₁₈ alkylethoxylated sulfate (“AES”) surfactant into the first high speed mixer,preferably in a weight ratio of from about 5:1 to about 1:5, and mostpreferably, in a range of from about 1:1 to about 3:1 (HLAS:AS). Theresult of such mixing is a “dry neutralization” reaction between theHLAS and the sodium carbonate embodied in the dry starting detergentmaterial, all of which forms agglomerates. It is preferable to add theHLAS before the addition of other surfactants such as AES or alkylsulfate (“AS”) surfactants so as to insure optimal mixing andneutralization of the HLAS in the first high speed mixer. Preferably,after agglomeration in the first high speed mixer, detergentagglomerates having a median particle size of from about 100 microns toabout 250 microns, more preferably from about 80 microns to about 140microns, and most preferably from about 90 microns to about 120 microns,are formed.

The rate of particle size growth can be controlled in a variety of ways,including but not limited to, varying the residence time, temperatureand mixing tool speed of the mixer, and controlling amount of liquid orbinder inputted into the mixer. In this regard, the particular parametercontrolled is not critical, but only that the median particle size fallswithin the ranges set forth previously. In this way, the smallerparticle sized starting detergent material is gradually built-up in acontrolled fashion such that the agglomerates have a large degree ofintragranule porosity, thereby resulting in a low density detergentcomposition. Stated differently, the smaller sized starting detergentmaterial is gently “glued” or “stuck” together to form porous built-upagglomerates, all of which is controlled so as to retain or increase theporosity by solidifying the particle bonds without consolidation orcollapse of the agglomerates.

In the second step of the process, the detergent agglomerates formed inthe first step are inputted into a second high speed mixer andagglomerated with a atomized liquid binder. The second high speed mixercan be the same piece of equipment as used in the first step or adifferent type of high speed mixer. For example, a Lödige CB mixer canbe used in the first step while a Schugi mixer is used in the secondstep. In this second process step, the agglomerates having medianparticle size as noted previously are mixed and built-up further in acontrolled fashion such that detergent agglomerates exiting the secondhigh speed mixer have a median particle size of from about 140 micronsto about 350 microns, more preferably from about 160 microns to about250 microns, and most preferably from about 180 microns to about 220microns. As in the first step of the process, the agglomerates areagglomerated in a very controlled fashion such that they have a medianparticle size within the aforementioned ranges. Again, the intragranuleporosity of the particles is increased by “sticking” together smallersized particles with a high degree of porosity between the particles(i.e., interparticle porosity). In this step, this is achieved byoperating the high speed mixer with sufficient binder atomization andspray coverage to produce only agglomerates in the aforementioned medianparticle size ranges. In this regard, an appropriate binder is added tofacilitate formation of the desired agglomerates in this step. Typicalbinders include liquid sodium silicate, a liquid acid precursor of ananionic surfactant such as HLAS, nonionic surfactant, polyethyleneglycol or mixtures thereof.

In the next step of the process, the built-up agglomerates are inputtedinto a fluid bed dryer in which the agglomerates are dried andagglomerated to a median particle size of from about 300 microns toabout 700 microns, more preferably from about 325 microns to about 450microns. The density of the agglomerates formed is from about 300 g/l toabout 550 g/l, more preferably from about 350 g/l to about 500 g/l, andeven more preferably from about 400 g/l to about 480 g/l. All of thesedensities are generally below that of typical detergent compositionsformed of dense agglomerates or most typical spray-dried granules.Preferably, in those process embodiments involving aqueous binders, theinlet air temperature of the fluid bed dryer is maintained in a range offrom about 100° C. to about 200° C. so as to enhance formation of thedesired agglomerates. While not wishing to be bound by theory, it isbelieved that this relatively high temperature insures rapid moistureevaporation to solidify the wet bonds of the built-up agglomerates so asto retain a high degree of intragranule porosity. As with the first andsecond steps of the process, the agglomerates are built-up from smallersizes to large sized particles having a high degree of intragranuleporosity. The degree of intragranule porosity is preferably from about20% to about 40%, and most preferably from about 25% to about 35%. Theintragranule porosity can be conveniently measured by standard mercuryporosimetry testing.

Optionally, a binder as described previously may be added during thisstep at more than one location such as at each end of the fluid beddryer so to enhance formation of the desired agglomerates. The netresult of this process embodiment involves addition of a binder in thesecond high speed mixer and at each end (i.e., the inlet port and exitport) of the fluid bed, thus totaling three binder addition points inthe process which provides superior low density agglomerates.Particularly preferred binders in this regard are liquid sodium silicateand HLAS.

Other optional steps contemplated by the present process includescreening the oversized detergent agglomerates in a screening apparatuswhich can take a variety of forms including but not limited toconventional screens chosen for the desired particle size of thefinished detergent product. Other optional steps include conditioning ofthe detergent agglomerates by subjecting the agglomerates to additionaldrying and/or cooling by way of apparatus discussed previously.

Another optional step of the instant process entails finishing theresulting detergent agglomerates by a variety of processes includingspraying and/or admixing other conventional detergent ingredients. Forexample, the finishing step encompasses spraying perfumes, brightenersand enzymes onto the finished agglomerates to provide a more completedetergent composition. Such techniques and ingredients are well known inthe art.

Detergent Surfactant Paste or Surfactant Acid Precursor

As mentioned, a liquid acid precursor of anionic surfactant is used inthe first step of the process as well as in the second and thirdessential steps of the process as a binder. This liquid acid precursorwill typically have a viscosity as measured at 30° C. of from about 500cps to about 5,000 cps. The liquid acid is a precursor for the anionicsurfactants described in more detail hereinafter. A detergent surfactantpaste can also be used in the process and is preferably in the form ofan aqueous viscous paste, although other forms are also contemplated bythe invention. This so-called viscous surfactant paste has a viscosityof from about 5,000 cps to about 100,000 cps, more preferably from about10,000 cps to about 80,000 cps, and contains at least about 10% water,more preferably at least about 20% water. The viscosity is measured at70° C. and at shear rates of about 10 to 100 sec.⁻¹. Furthermore, thesurfactant paste, if used, preferably comprises a detersive surfactantin the amounts specified previously and the balance water and otherconventional detergent ingredients.

The surfactant itself, in the viscous surfactant paste, is preferablyselected from anionic, nonionic, zwitterionic, ampholytic and cationicclasses and compatible mixtures thereof. Detergent surfactants usefulherein are described in U.S. Pat. No. 3,664,961, Norris, issued May 23,1972, and in U.S. Pat. No. 3,919,678, Laughlin et al, issued Dec. 30,1975, both of which are incorporated herein by reference. Usefulcationic surfactants also include those described in U.S. Pat. No.4,222,905, Cockrell, issued Sep. 16, 1980, and in U.S. Pat. No.4,239,659, Murphy, issued Dec. 16, 1980, both of which are alsoincorporated herein by reference. Of the surfactants, anionics andnonionics are preferred and anionics are most preferred.

Nonlimiting examples of the preferred anionic surfactants useful in thesurfactant paste, or from which the liquid acid precursor describedherein derives, include the conventional C₁₁-C₁₈ alkyl benzenesulfonates (“LAS”), primary, branched-chain and random C₁₀-C₂₀ alkylsulfates (“AS”), the C₁₀-C₁₈ secondary (2,3) alkyl sulfates of theformula CH₃(CH₂)_(x)(CHOSO₃ ⁻M⁺) CH₃ and CH₃ (CH₂)_(y)(CHOSO₃ ⁻M⁺)CH₂CH₃where x and (y+1) are integers of at least about 7, preferably at leastabout 9, and M is a water-solubilizing cation, especially sodium,unsaturated sulfates such as oleyl sulfate, and the C₁₀-C₁₈ alkyl alkoxysulfates (“AE_(x)S”; especially EO 1-7 ethoxy sulfates).

Optionally, other exemplary surfactants useful in the paste of theinvention include and C₁₀-C₁₈ alkyl alkoxy carboxylates (especially theEO 1-5 ethoxycarboxylates), the C₁₀₋₁₈ glycerol ethers, the C₁₀-C₁₈alkyl polyglycosides and their corresponding sulfated polyglycosides,and C₁₂-C₁₈ alpha-sulfonated fatty acid esters. If desired, theconventional nonionic and amphoteric surfactants such as the C₁₂-C₁₈alkyl ethoxylates (“AE”) including the so-called narrow peaked alkylethoxylates and C₆-C₁₂ alkyl phenol alkoxylates (especially ethoxylatesand mixed ethoxy/propoxy), C₁₂-C₁₈ betaines and sulfobetaines(“sultaines”), C₁₀-C₁₈ amine oxides, and the like, can also be includedin the overall compositions. The C₁₀-C₁₈ N-alkyl polyhydroxy fatty acidamides can also be used. Typical examples include the C₁₂-C₁₈N-methylglucamides. See WO 9,206,154. Other sugar-derived surfactantsinclude the N-alkoxy polyhydroxy fatty acid amides, such as C₁₀-C₁₈N-(3-methoxypropyl) glucamide. The N-propyl through N-hexyl C₁₂-C₁₈glucamides can be used for low sudsing. C₁₀-C₂₀ conventional soaps mayalso be used. If high sudsing is desired, the branched-chain C₁₀-C₁₆soaps may be used. Mixtures of anionic and nonionic surfactants areespecially useful. Other conventional useful surfactants are listed instandard texts.

Dry Detergent Material

The starting dry detergent material of the present process preferablycomprises a builder and other standard detergent ingredients such assodium carbonate, especially when a liquid acid precursor of asurfactant is used as it is needed as a neutralizing agent in the firststep of the process. Thus, preferable starting dry detergent materialincludes sodium carbonate and a phosphate or an aluminosilicate builderwhich is referenced as an aluminosilicate ion exchange material. Apreferred builder is selected from the group consisting ofaluminosilicates, crystalline layered silicates, phosphates, carbonatesand mixtures thereof. Preferred phosphate builders include sodiumtripolyphosphate, tetrasodium pyrophosphate and mixtures thereof.Additional specific examples of inorganic phosphate builders are sodiumand potassium tripolyphosphate, pyrophosphate, polymeric metaphosphatehaving a degree of polymerization of from about 6 to 21, andorthophosphates. Examples of polyphosphonate builders are the sodium andpotassium salts of ethylene diphosphonic acid, the sodium and potassiumsalts of ethane 1-hydroxy-1, 1-diphosphonic acid and the sodium andpotassium salts of ethane, 1,1,2-triphosphonic acid. Other phosphorusbuilder compounds are disclosed in U.S. Pat. Nos. 3,159,581; 3,213,030;3,422,021; 3,422,137; 3,400,176 and 3,400,148, all of which areincorporated herein by reference.

The aluminosilicate ion exchange materials used herein as a detergentbuilder preferably have both a high calcium ion exchange capacity and ahigh exchange rate. Without intending to be limited by theory, it isbelieved that such high calcium ion exchange rate and capacity are afunction of several interrelated factors which derive from the method bywhich the aluminosilicate ion exchange material is produced. In thatregard, the aluminosilicate ion exchange materials used herein arepreferably produced in accordance with Corkill et al, U.S. Pat. No.4,605,509 (Procter & Gamble), the disclosure of which is incorporatedherein by reference.

Preferably, the aluminosilicate ion exchange material is in “sodium”form since the potassium and hydrogen forms of the instantaluminosilicate do not exhibit the as high of an exchange rate andcapacity as provided by the sodium form. Additionally, thealuminosilicate ion exchange material preferably is in over dried formso as to facilitate production of crisp detergent agglomerates asdescribed herein. The aluminosilicate ion exchange materials used hereinpreferably have particle size diameters which optimize theireffectiveness as detergent builders. The term “particle size diameter”as used herein represents the average particle size diameter of a givenaluminosilicate ion exchange material as determined by conventionalanalytical techniques, such as microscopic determination and scanningelectron microscope (SEM). The preferred particle size diameter of thealuminosilicate is from about 0.1 micron to about 10 microns, morepreferably from about 0.5 microns to about 9 microns. Most preferably,the particle size diameter is from about 1 microns to about 8 microns.

Preferably, the aluminosilicate ion exchange material has the formula

Na_(z)[(AlO₂)_(z).(SiO₂)_(y)]xH₂O

wherein z and y are integers of at least 6, the molar ratio of z to y isfrom about 1 to about 5 and x is from about 10 to about 264. Morepreferably, the aluminosilicate has the formula

Na₁₂[(AlO₂)₁₂.(SiO₂)₁₂]xH₂O

wherein x is from about 20 to about 30, preferably about 27. Thesepreferred aluminosilicates are available commercially, for example underdesignations Zeolite A, Zeolite B and Zeolite X. Alternatively,naturally-occurring or synthetically derived aluminosilicate ionexchange materials suitable for use herein can be made as described inKrummel et al, U.S. Pat. No. 3,985,669, the disclosure of which isincorporated herein by reference.

The aluminosilicates used herein are further characterized by their ionexchange capacity which is at least about 200 mg equivalent of CaCO₃hardness/gram, calculated on an anhydrous basis, and which is preferablyin a range from about 300 to 352 mg equivalent of CaCO₃ hardness/gram.Additionally, the instant aluminosilicate ion exchange materials arestill further characterized by their calcium ion exchange rate which isat least about 2 grains Ca⁺⁺/gallon/minute/−gram/gallon, and morepreferably in a range from about 2 grainsCa⁺⁺/gallon/minute/−gram/gallon to about 6 grainsCa⁺⁺/gallon/minute/−gram/gallon.

Adjunct Detergent Ingredients

The starting dry detergent material in the present process can includeadditional detergent ingredients and/or, any number of additionalingredients can be incorporated in the detergent composition duringsubsequent steps of the present process. These adjunct ingredientsinclude other detergency builders, bleaches, bleach activators, sudsboosters or suds suppressors, anti-tarnish and anticorrosion agents,soil suspending agents, soil release agents, germicides, pH adjustingagents, non-builder alkalinity sources, chelating agents, smectiteclays, enzymes, enzyme-stabilizing agents and perfumes. See U.S. Pat.No. 3,936,537, issued Feb. 3, 1976 to Baskerville, Jr. et al.,incorporated herein by reference.

Other builders can be generally selected from the various borates,polyhydroxy sulfonates, polyacetates, carboxylates, citrates, tartratemono- and di-succinates, and mixtures thereof. Preferred are the alkalimetal, especially sodium, salts of the above. In comparison withamorphous sodium silicates, crystalline layered sodium silicates exhibita clearly increased calcium and magnesium ion exchange capacity. Inaddition, the layered sodium silicates prefer magnesium ions overcalcium ions, a feature necessary to insure that substantially all ofthe “hardness” is removed from the wash water. These crystalline layeredsodium silicates, however, are generally more expensive than amorphoussilicates as well as other builders. Accordingly, in order to provide aneconomically feasible laundry detergent, the proportion of crystallinelayered sodium silicates used must be determined judiciously.

The crystalline layered sodium silicates suitable for use hereinpreferably have the formula

NaMSi_(x)O_(2x+1).yH₂O

wherein M is sodium or hydrogen, x is from about 1.9 to about 4 and y isfrom about 0 to about 20. More preferably, the crystalline layeredsodium silicate has the formula

NaMSi₂O₅.yH₂O

wherein M is sodium or hydrogen, and y is from about 0 to about 20.These and other crystalline layered sodium silicates are discussed inCorkill et al, U.S. Pat. No. 4,605,509, previously incorporated hereinby reference.

Examples of nonphosphorus, inorganic builders are tetraboratedecahydrate and silicates having a weight ratio of SiO₂ to alkali metaloxide of from about 0.5 to about 4.0, preferably from about 1.0 to about2.4. Water-soluble, nonphosphorous organic builders useful hereininclude the various alkali metal, ammonium and substituted ammoniumpolyacetates, carboxylates, polycarboxylates and polyhydroxy sulfonates.Examples of polyacetate and polycarboxylate builders are the sodium,potassium, lithium, ammonium and substituted ammonium salts of ethylenediamine tetraacetic acid, nitrilotriacetic acid, oxydisuccinic acid,mellitic acid, benzene polycarboxylic acids, and citric acid.

Polymeric polycarboxylate builders are set forth in U.S. Pat. No.3,308,067, Diehl, issued Mar. 7, 1967, the disclosure of which isincorporated herein by reference. Such materials include thewater-soluble salts of homo- and copolymers of aliphatic carboxylicacids such as maleic acid, itaconic acid, mesaconic acid, fumaric acid,aconitic acid, citraconic acid and methylene malonic acid. Some of thesematerials are useful as the water-soluble anionic polymer as hereinafterdescribed, but only if in intimate admixture with the non-soap anionicsurfactant.

Other suitable polycarboxylates for use herein are the polyacetalcarboxylates described in U.S. Pat. No. 4,144,226 issued Mar. 13, 1979to Crutchfield et al, and U.S. Pat. No. 4,246,495, issued Mar. 27, 1979to Crutchfield et al, both of which are incorporated herein byreference. These polyacetal carboxylates can be prepared by bringingtogether under polymerization conditions an ester of glyoxylic acid anda polymerization initiator. The resulting polyacetal carboxylate esteris then attached to chemically stable end groups to stabilize thepolyacetal carboxylate against rapid depolymerization in alkalinesolution, converted to the corresponding salt, and added to a detergentcomposition. Particularly preferred polycarboxylate builders are theether carboxylate builder compositions comprising a combination oftartrate monosuccinate and tartrate disuccinate described in U.S. Pat.No. 4,663,071, Bush et al., issued May 5, 1987, the disclosure of whichis incorporated herein by reference.

Bleaching agents and activators are described in U.S. Pat. No.4,412,934, Chung et al., issued Nov. 1, 1983, and in U.S. Pat. No.4,483,781, Hartman, issued Nov. 20, 1984, both of which are incorporatedherein by reference. Chelating agents are also described in U.S. Pat.No. 4,663,071, Bush et al., from Column 17, line 54 through Column 18,line 68, incorporated herein by reference. Suds modifiers are alsooptional ingredients and are described in U.S. Pat. Nos. 3,933,672,issued Jan. 20, 1976 to Bartoletta et al., and 4,136,045, issued Jan.23, 1979 to Gault et al., both incorporated herein by reference.

Suitable smectite clays for use herein are described in U.S. Pat. No.4,762,645, Tucker et al, issued Aug. 9, 1988, Column 6, line 3 throughColumn 7, line 24, incorporated herein by reference. Suitable additionaldetergency builders for use herein are enumerated in the Baskervillepatent, Column 13, line 54 through Column 16, line 16, and in U.S. Pat.No. 4,663,071, Bush et al, issued May 5, 1987, both incorporated hereinby reference.

In order to make the present invention more readily understood,reference is made to the following example, which is intended to beillustrative only and not intended to be limiting in scope.

EXAMPLE

This Example illustrates the process invention in which a low densityagglomerated detergent composition is prepared. A Lödige CB 30 highspeed mixer is charged with a mixture of powders, namely sodiumcarbonate (median particle size 15 microns) and sodium tripolyphosphate(“STPP”) with a median particle size of 25 microns. A liquid acidprecursor of sodium alkylbenzene sulfonate surfactant (C₁₂H₂₅—C₆H₄—SO₃—Hor “HLAS” as noted below) and a C₁₀₋₁₈ alkyl ethoxylated sulfate aqueoussurfactant paste (EO=3, 70% active “AES”) are also inputted into theLödige CB 30 mixer, wherein the HLAS is added first. The mixer isoperated at 1600 rpm and the sodium carbonate, STPP, HLAS and AES areformed into agglomerates having a median particle size of about 110microns after a mean residence time in the Lödige CB 30 mixer of about 5seconds. The agglomerates are then fed to a Schugi (Model # FX160) highspeed mixer which is operated at 2800 rpms with mean residence time ofabout 2 seconds. A HLAS binder is inputted into the Schugi (Model #FX160) mixer during this step which results in built-up agglomerateshaving a median particle size of about 180 microns being formed.Thereafter, the built-up agglomerates are passed through a four-zonefluid bed dryer wherein two spray nozzles are positioned in the firstand fourth zone of the fluid bed dryer. The fluid bed is operated at anair inlet temperature of about 125° C. In the amounts and particle sizespecified below, fines are also added to the Lödige CB 30 mixer. In thefirst and fourth zones of the fluid bed dryer, liquid sodium silicate isfed into the fluid bed dryer resulting in the finished detergentagglomerates having a density of about 485 g/l and a median particlesize of about 360 microns. Unexpectedly, the finished agglomerates haveexcellent physical properties in that they are free flowing as exhibitedby their superior cake strength grades.

The composition of the agglomerates are given below in Table I.

TABLE I (% weight) Component I LAS (Na) 15.8 AES (EO = 3) 4.7 Sodiumcarbonate 48.0 STPP 22.7 Sodium Silicate 5.5 Water 3.3 100.0

The agglomerates embody about 14% of the fines (less than 150 microns)mentioned previously which are recycled from the fluid bed back into theLödige CB 30 to enhance production of the agglomerates produced by theprocess.

Having thus described the invention in detail, it will be clear to thoseskilled in the art that various changes may be made without departingfrom the scope of the invention and the invention is not to beconsidered limited to what is described in the specification.

What is claimed is:
 1. A process for preparing a low density detergentcomposition characterized by the steps of: (a) agglomerating a detergentsurfactant paste or precursor thereof and dry starting detergentmaterial having a median particle size in a range from 5 microns to 70microns in a first high speed mixer to obtain agglomerates having amedian particle size of from 100 microns to 250 microns; (b) mixing saiddetergent agglomerates with a first binder in a high speed mixer toobtain built-up agglomerates having a median particle size in a range offrom 140 microns to 350 microns; and (c) feeding said built-upagglomerates into a fluid bed dryer in which built-up agglomerates areagglomerated with a second binder and dried to form detergentagglomerates having a median particle size in a range of from 300microns to 700 microns and a density in a range from 300 g/l to 550 g/l.2. The process of claim 1 wherein said first binder is sodium silicate.3. The process of claim 1 wherein said first binder and said secondbinder are a liquid acid precursor of an anionic surfactant.
 4. Theprocess of claim 1 wherein the intragranule porosity of said detergentagglomerates is from 20% to 40%.
 5. The process of claim 1 wherein saidfirst binder and said second binder are sodium silicate.
 6. The processof claim 1 wherein said step (a) includes agglomerating a liquid acidprecursor of C₁₁₋₁₈ linear alkylbenzene sulfonate surfactant and aC₁₀₋₁₈ alkyl ethoxylated sulfate surfactant.
 7. The process of claim 1wherein said step (c) includes maintaining the temperature of said fluidbed dryer to be in a range of from 100° C. to 200° C.
 8. The process ofclaim 1 wherein said dry starting material comprises a builder selectedfrom the group consisting of aluminosilicates, crystalline layeredsilicates, phosphates, carbonates and mixtures thereof.
 9. A process forpreparing a low density detergent composition comprising the steps of:(a) agglomerating a first liquid acid precursor of an anionic surfactantand dry starting detergent material having a median particle size in arange from about 5 microns to about 70 microns in a first high speedmixer to obtain detergent agglomerates having a median particle size offrom about 100 microns to about 250 microns; (b) mixing said detergentagglomerates with a second liquid acid precursor of an anionicsurfactant in a second high speed mixer to obtain built-up agglomerateshaving a median particle size in a range of from about 140 microns toabout 350 microns; and (c) feeding said built-up agglomerates into afluid bed dryer in which said built-up agglomerates are agglomeratedwith a third liquid acid precursor of an anionic surfactant and dried toform agglomerates having a median particle size in a range of from about300 microns to about 700 microns and a density in a range from about 300g/l to about 550 g/l.
 10. The process of claim 9 wherein said first,second and third liquid acid precursors of an anionic surfactant areacid precursors of C₁₂₋₁₄ linear alkylbenzene sulfonate surfactant. 11.The process of claim 9 further comprising adding C₁₀₋₁₈ alkylethoxylated sulfate surfactant to said high speed mixer.
 12. The processof claim 9 wherein said step (c) includes maintaining the temperature ofsaid fluid bed dryer to be in a range of from about 100° C. to about200° C.
 13. The process of claim 9 wherein said dry starting detergentmaterial having a median particle size in a range from about 20 micronsto about 50 microns.
 14. The process of claim 9 wherein said detergentagglomerates have a density of from about 350 g/l to about 500 g/l. 15.The process of claim 9 wherein said dry starting material comprises abuilder selected from the group consisting of aluminosilicates,crystalline layered silicates, phosphates, and mixtures thereof.